Back pain is a common health problem among pregnant women. Back pain can have important adverse consequences including a reduced quality of life and a reduced ability to function well both at work and at home. Given that many women prefer to avoid taking medications during pregnancy it is useful to consider non-pharmacological approaches to minimizing back pain and improving quality of life. Moderate intensity resistance exercise training offers a plausibly effective method for attenuating back pain among pregnant women. The broad objective of this project is to further our understanding of the health consequences of moderate intensity resistance exercise training for pregnant women. Moderate intensity aerobic exercise has been found to be safe and healthful for pregnant women, but little is known about the health effects of moderate intensity resistance exercise. Accordingly, the specific aims of the proposed research are to test the hypotheses that: (1) 16 weeks of moderate intensity resistance exercise training of the legs, back, abdominal and truck musculature performed twice weekly during the second and third trimesters will significantly attenuate back pain; (2) the resistance exercise training program will significantly attenuate pregnancy-induced loss of back function; and (3) the resistance exercise training program will significantly improve pain-related quality of life. To accomplish these goals 180 healthy pregnant women with back pain will be recruited to begin participating during the first two months of their second trimester. The participants will be randomized to perform sixteen weeks of either a supervised twice weekly, moderate intensity resistance exercise program, a pregnancy-related education program (i.e., placebo condition), or a waiting list control condition. Valid measures of back pain, back function and pain-related quality of life will be used to test the outcome of the randomized controlled trial. There is an urgent need to learn more about the health consequences of resistance exercise training among pregnant women in part because women increasingly are performing resistance exercise during their pregnancy. Unfortunately, at the present time there is a lack of scientific information available to nurses, physicians and other health professionals concerning the health outcomes associated with moderate intensity resistance exercise training among pregnant women. [unreadable] [unreadable] [unreadable]